FRONTLINE doctors in Scotland have hit out at the "Kafkaesque" system of fitness-to-work benefits assessments which they say is placing their most vulnerable patients at risk of suicide.

A campaign has been set up, backed by more than 40 leading medics and charities, to encourage GPs to use little-known regulations to challenge cases where declaring patients fit to work, under the benefits assessment system, would place them in danger of physical or mental harm.

The Sunday Herald can also reveal Scottish ministers have written to Work and Pensions Secretary Iain Duncan Smith, calling for urgent research to be undertaken on the impact of benefit reform on both claimants and the NHS.

Yesterday, the British Medical Association Scotland issued a warning that GPs are being "flooded with additional avoidable work" as patients seek medical evidence to support benefit claims.

The letter from Deputy First Minister Nicola Sturgeon and Health Secretary Alex Neil highlights concerns the system will come under "intolerable strain" as further reforms come into effect.

The controversial tests see patients assessed by the private French firm Atos on whether or not they are fit for work or can still draw benefits.

Dr Stephen Carty, medical adviser for Scottish-based disability rights group Black Triangle and a GP in Edinburgh, said he had been "absolutely staggered" by some of the patients who had been told they should be employed following work capability assessments.

He said in many cases they had severe conditions which could not be helped by medication, or were in the latter stages of advanced disease with a shortened life expectancy.

Carty said: "I have had five patients who have had a serious attempt at taking their own life, where in my view, the fear related to a workplace capability assessment – or the outcome of the decision – was a significant contributory factor. "

He said he was concerned patients – who may lack communication skills or understanding of their condition – had to submit forms, while their GP was often not approached by the Department for Work and Pensions (DWP) for medical details.

"By the way that one patient filled out his form you would get the impression there was nothing wrong," he said. "But he had lacked insight into the fact he was schizophrenic. No information was requested from me and he was found fit for work, yet he had spent months on a locked ward and was still firmly of the opinion he was the Messiah."

The campaign by Black Triangle has been backed by 25 doctors, including leading GPs, psychiatrists and neurologists. Other supporters are Mark Serwotka, general secretary of the Public and Commercial Services Union and Len McCluskey head of Unite.

Union chiefs from the National Union of Teachers, the National Union of Journalists, the University and College Union, and Unison also backed the campaign, alongside Phil Gray, chief executive of the Chartered Society of Physiotherapy.

A letter signed by the supporters states that doctors are "witnessing daily the enormous avoidable suffering of many of our most vulnerable patients caught up in this Kafkaesque system of 'disability assessment'".

The letter calls on the British Medical Association (BMA) to help publicise two little-known Employment and Support (ESA) 2013 regulations, which a doctor can use to flag up cases where there is a substantial risk "to the mental or physical health of any person" if the claimant is found fit for work.

Among those who have backed the campaign is Dr Chris Johnstone, a GP based in Paisley, who said he had seen a number of cases where people who had been deemed fit to work were clearly not capable of taking up employment.

"There were a lesser number of people who probably were fit to work," he said. "But we saw many more people who seemed to be unfairly treated."

Johnstone said problems existed particularly with patients suffering mental-health problems being told they were fit to work.

"One of the problems is these people don't come and get help, they just accept the decision believing that is the right one," he said. "I have had a couple of patients who said I have always done what the state tells me, so it must be right."

He said he believed such circumstances had contributed to one of his patients ending up in a psychiatric hospital, while another had a heart attack.

Trades unions and charities supporting doctors say the current system is "unfit for purpose" and poses a "real risk" to the health of disabled people and those with life-threatening conditions.

Bill Scott, manager of disability campaign group Inclusion Scotland, said: "We know of people who are reporting suicidal feelings at just the prospect of having an assessment. There are people who have gone through the assessment, been found fit for work, appealed, won their appeal and then been sent back into the system with another assessment that finds them fit for work again. They feel they are on a never ending treadmill."

A spokeswoman for the DWP said: "A decision on whether someone is well enough to work is taken following a thorough assessment and after careful consideration of all the available evidence. That can include supporting medical evidence from the claimant's GP or other healthcare professional.

"GPs have been clear they do not want to be responsible for making decisions on people's benefit entitlement, which is why we have processes in place to request the appropriate information from GPs to enable us to make those decisions."